Stirling, Ericsson, turbine, and minto wheel.
In terms of yields when operating in a thermal machine, I just know that the Tesla turbines announced attractive yields for fairly low temperatures (300 to 800 ° C), ideal for linear solar traps, but I do not have the numbers handy.
As for the reymondo focal concentration trap, the Stirling can be interesting for its relative simplicity and its good performance over the envisaged heat range: around 1000 ° C, it should theoretically pass the 60% of yields. In practice, the best stirling engine produced of which I have the figures is a Stirling engine of Swedish submarine, with real yields of 42% ... Much less than the ultra-slow diesels mentioned above ...
We will have to see if there is not a possibility of adapting the diesel cycle to an "external combustion"?
I don't believe it but we sometimes have surprises ...